There is know a blood vessel function inspecting apparatus for measuring a blood flow velocity distribution within a blood vessel, by ultrasonic Doppler effect measurement. Patent Document 1 discloses an example of such a blood vessel function inspecting apparatus. The blood vessel function inspecting apparatus disclosed in this Patent Document 1 is configured to calculate a blood viscosity distribution and a blood shear rate distribution within the blood vessel, on the basis of the blood flow velocity distribution measured as described above. The blood vessel function inspecting apparatus is further configured to calculate a blood shear stress distribution on the basis of the calculated blood viscosity distribution and blood shear rate distribution. The calculation of the above-described blood viscosity distribution by the blood vessel function inspecting apparatus on the basis of the above-described blood flow velocity distribution is implemented by calculation according to the well known Navier-Stokes equations.
In the well known FMD inspection, a change ratio of the diameter of the blood vessel after releasing of the blood vessel from blood flow obstruction is measured. It is know that a change (an increase) of the diameter of the blood vessel is caused by a stimulus in the form of a shear stress. In this respect, the detection of the above-described shear stress is effective to implement the FMD inspection. Patent Document 2 discloses a blood vessel function inspecting apparatus configured to calculate the above-described shear stress for the FMD inspection.